(Reuters) - Adult film sets throughout the Los Angeles area have shut down indefinitely after a porn actress tested positive for HIV, the trade association for the industry said on Thursday.

The actress, who works under the name Cameron Bay, has contracted the virus that causes AIDS, the Free Speech Coalition said in a press release.

The trade group said film producers called a moratorium on production late on Wednesday and that filming would not resume until all of Bay's partners are notified and tested.

The incident comes amid continued opposition on the part of many companies that produce adult films to a recently enacted law in Los Angeles County that requires porn actors to use condoms on the set.

The multibillion-dollar adult film industry is centered in the San Fernando Valley area of Los Angeles.

Michael Weinstein, head of the Los Angeles-based AIDS Healthcare Foundation and a backer of the condom law, said he suspects that Bay contracted the virus on a set.

Last month, he said, the actress tested negative for HIV, and this month, she tested positive. In one film that she worked on between the tests, it appears that condoms were not used, Weinstein said.

"It's a tragedy for her," he said. "Obviously she was infected by someone."

The industry group said there was "no evidence whatsoever" that Bay was infected on a set, or that others were exposed to the virus while performing sex scenes with her.

Bay said she planned to cooperate with public health officials as they try to track down her sex partners to find out who might have infected her, and whether she infected anyone.

"As difficult as this news is for me today, I am hopeful that no other performers have been affected," Bay said in a statement. "I plan on doing everything possible to assist the medical professionals and my fellow performers."